Particularly in the glass molding industry, cooling of the molds in order to control the rate of solidification of the molten glass is a critical factor in determining the quality of the molded product and is integrally related to the speed of operation of the molding machine. Due to the difficulty in controlling liquid cooling in this environment, most of the industry has employed air cooling of the molds but this is very inefficient. In this case of multi cavity bottle molding machines, it requires very large blowers which when electrically driven employ motors in the range of 250 horsepower per machine. In order to increase the speed of operation of the molding machines, it has been considered desirable to utilize liquid cooling of the molds but prior art attempts in this direction have resulted in too rapid chilling of the molds and consequently poor quality molded products.